It is particularly preferred to employ Staphylococcal genes and gene products as targets for the development of antibiotics. The Staphylococci make up a medically important genera of microbes. They are known to produce two types of disease, invasive and toxigenic. Invasive infections are characterized generally by abscess formation effecting both skin surfaces and deep tissues. S. aureus is the second leading cause of bacteremia in cancer patients. Osteomyelitis, septic arthritis, septic thrombophlebitis and acute bacterial endocarditis are also relatively common. There are at least three clinical conditions resulting from the toxigenic properties of Staphylococci. The manifestation of these diseases result from the actions of exotoxins as opposed to tissue invasion and bacteremia. These conditions include: Staphylococcal food poisoning, scalded skin syndrome and toxic shock syndrome.
Riboflavin (vitamin B2) is a member of the B complex of vitamins which function as coenzymes in metabolic reactions. Riboflavin has two coenzyme forms, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) which act in oxidation-reduction reactions such as the cytochrome system of electron transport and the oxidative degradation of pyruvate, fatty acids and amino acids. The first committed step in the biosynthesis of riboflavin is the opening of the imidazole ring of GTP. In the presence of 3 H.sub.2 O and Mg.sup.++, the C-8 of GTP is released as formate accompanied by the release of pyrophosphate by the action of GTP cyclohyrolase II (GCH2; EC 3.5.4.25). This enzyme function is encoded by ribA in bacteria and ribl in yeast species. Through a series of steps, involving 3,4-dihydroxy-2-butanone 4 phosphate synthase (ribA), 6,7-dimethyl-8-ribityllumazine synthase (ribH), riboflavin synthase (ribB), pyrimidine deaminase and pyrimidine reductase (ribG), enzymes encoded by genes within the riboflavin biosynthesis operon, riboflavin is formed. Because the genes required for riboflavin biosynthesis are present in many pathogenic microorganisms, and since riboflavin biosynthesis has shown to be required for virulence in the swine pathogen Actinobacillus pleuropneumoniae (Fuller, T E, et al. (1996) A riboflavin auxotroph of Actinobacillus pleuropneumoniae is attenuated in swine. Infect. Immun. 64:4659-4664), these gen e products represent broad spectrum antibacterial as well as antifungal targets.
The frequency of Staphylococcus aureus infections has risen dramatically in the past few decades. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Staphylococcus aureus strains which are resistant to some or all of the standard antibiotics. This phenomenon has created a demand for both new anti-microbial agents, vaccines, and diagnostic tests for this organism.
Clearly, there exists a need for factors, such as the ribG embodiments of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists to find ways to prevent, ameliorate or correct such infection, dysfunction and disease.
Certain of the polypeptides of the invention possess amino acid sequence homology to a known Bacillus subtilis ribG protein.